To achieve a high degree of proficiency in the sport of bowling, it is essential that the ball properly and comfortably fits the hand of the individual bowler and that a ball weight be chosen which suits the strength and ability of that individual. Slight variations in the fit and weight can have a significant effect upon the consistency, accuracy, speed and degree of hook of the ball.
Presently, the most common means for selecting the fit involves the use of a spherical bowling ball assembly having two sections, rotatable relative to each other, each section including numerous holes for insertion of the thumb and bowling fingers. The bowler inserts each of his bowling fingers and thumb into the various holes until he selects ones which appear to have a proper degree of clearance, or from which the proper hole diameter may be estimated. Having done so, he then reinserts his thumb into the hole most closely approximating his size, and rotates the opposite section of the assembly until he locates two adjacent finger holes thereon most closely approximating a comfortable span for his hand. The selected ball is then drilled to those span and hole diameter specifications.
The above device, and other prior art devices, are limited in the choices of hole diameters and spans from which to determine the bowlers fit, and the bowler has no way of trying out the specified fit before his own personal ball is drilled. Also, the prior art methods do not provide means for selecting balls with a weight imbalance across any plane through the center of the ball. Such imbalances are desirable in altering the degree of hook and impact action of the ball. Thus, oftentimes, after the ball is drilled, a bowler is dissatisfied with the fit or the balance and their effect on his performance on the bowling lane.